1. Field of the Invention
The present invention relates to processing tire pressure monitor (TPM) data signals.
2. Background Art
It is challenging to use amplitude shift key (ASK) modulation in the transmission of tire pressure monitor (TPM) signals from a tire to an electronic control unit (ECU) because of residual amplitude modulation (AM). As the tire spins, the signal amplitude varies and interferes with the ability of an associate receiver to decode (slice) signals (data) transmitted from the TPM.
The root cause for the problem is that the average bit value at the data slicer does not change fast enough to keep up with the rapidly changing data amplitude due to the slow nature of the RC circuit that accomplishes the averaging for the reference. The end effect is that the current data slicer reference is actually relevant more to the previous data bit than to the current one. However, it is desirable to use ASK because of the significant improvement in battery life that can be obtained along with 6dB higher peak power allowed by the FCC (on average).